HSC Survey Results

German Bank Survey # 1 Results from 04/08/2024

Survey Details

6 commercial purse seiners conducted this fishing survey on 04/08/2024 starting at 20:00:00.

All vessels ran two transects in the German Bank box and two transect in the Seal Island Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Janice II.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for German Bank using standardized parallel transects is 12,233mt. The preliminary biomass estimate for Seal Island is 45,930mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
C1 T01 2024-08-04 19:55:39 2024-08-04 22:23:13 -66.446 43.565 -66.448 43.235 GB 40.90 8.98
C1 T02 2024-08-04 23:01:13 2024-08-05 01:28:30 -66.310 43.236 -66.309 43.568 GB 40.78 8.97
C1 T03 2024-08-05 02:01:53 2024-08-05 03:52:40 -66.211 43.500 -66.207 43.248 GB 30.72 8.99
C1 T04 2024-08-05 04:07:20 2024-08-05 05:57:58 -66.154 43.251 -66.153 43.501 GB 31.03 9.09
FM T01 2024-08-04 20:58:10 2024-08-04 23:28:33 -66.470 43.565 -66.470 43.234 GB 39.23 8.45
FM T02 2024-08-05 00:09:40 2024-08-05 02:32:25 -66.332 43.237 -66.332 43.568 GB 38.66 8.77
FM T03 2024-08-05 03:08:55 2024-08-05 04:56:12 -66.220 43.501 -66.221 43.246 GB 29.64 8.95
FM T04 2024-08-05 05:11:35 2024-08-05 07:01:31 -66.164 43.246 -66.164 43.503 GB 29.93 8.82
LB T01 2024-08-04 19:45:40 2024-08-04 22:33:03 -66.402 43.566 -66.401 43.234 GB 38.99 7.55
LB T02 2024-08-04 23:19:55 2024-08-05 01:32:43 -66.263 43.235 -66.263 43.565 GB 37.82 9.23
LB T03 2024-08-05 02:04:53 2024-08-05 03:47:54 -66.193 43.502 -66.192 43.248 GB 29.08 9.14
LB T04 2024-08-05 04:06:59 2024-08-05 06:16:00 -66.134 43.248 -66.135 43.502 GB 29.56 7.42
LJ T01 2024-08-04 19:49:31 2024-08-04 22:19:14 -66.378 43.567 -66.378 43.234 GB 37.11 8.03
LJ T02 2024-08-04 23:01:05 2024-08-05 01:23:10 -66.240 43.234 -66.240 43.568 GB 37.11 8.46
LJ T03 2024-08-05 01:52:43 2024-08-05 03:40:50 -66.182 43.502 -66.182 43.248 GB 28.22 8.46
LJ T04 2024-08-05 03:56:00 2024-08-05 05:52:19 -66.125 43.248 -66.125 43.509 GB 29.08 8.10
LM T01 2024-08-04 19:41:44 2024-08-04 22:08:03 -66.492 43.567 -66.499 43.233 GB 38.14 8.44
LM T02 2024-08-04 22:48:18 2024-08-05 01:12:38 -66.355 43.232 -66.356 43.567 GB 38.18 8.57
LM T03 2024-08-05 01:50:27 2024-08-05 03:37:00 -66.230 43.500 -66.230 43.248 GB 28.67 8.72
LM T04 2024-08-05 03:51:42 2024-08-05 05:41:19 -66.172 43.249 -66.173 43.502 GB 28.82 8.52
MS T01 2024-08-04 19:44:23 2024-08-04 22:30:32 -66.424 43.566 -66.424 43.237 GB 41.47 8.09
MS T02 2024-08-04 23:18:30 2024-08-05 01:34:05 -66.286 43.238 -66.286 43.565 GB 39.74 9.50
MS T03 2024-08-05 02:09:06 2024-08-05 03:52:56 -66.201 43.500 -66.201 43.249 GB 30.02 9.37
MS T04 2024-08-05 04:15:20 2024-08-05 06:18:00 -66.144 43.253 -66.144 43.503 GB 32.00 8.45

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
LB T03 -35.5 -37.763 0.594
LJ T03 -35.5 -38.675 0.481
LM T04 -35.5 -40.261 0.334
C1 T04 -35.5 -41.888 0.230
LM T03 -35.5 -41.935 0.227
LM T02 -35.5 -42.523 0.198
MS T03 -35.5 -42.634 0.193
LM T01 -35.5 -42.758 0.188
MS T01 -35.5 -42.974 0.179
FM T03 -35.5 -43.097 0.174
FM T04 -35.5 -43.178 0.171
C1 T01 -35.5 -45.771 0.094
FM T01 -35.5 -47.661 0.061
LJ T04 -35.5 -47.760 0.059
C1 T03 -35.5 -47.938 0.057
LJ T01 -35.5 -49.467 0.040
MS T04 -35.5 -50.463 0.032
MS T02 -35.5 -51.855 0.023
C1 T02 -35.5 -53.188 0.017
FM T02 -35.5 -54.675 0.012
LB T01 -35.5 -55.332 0.010
LB T04 -35.5 -56.874 0.007
LJ T02 -35.5 -57.144 0.007
LB T02 -35.5 -61.557 0.002
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
German Bank -35.5 803.4513 -53.6742 0.0151 12,233 74.1 21 3,064.51 25.05
Seal Island -35.5 281.1445 -43.3683 0.1674 45,930 25.9 79 18,767.20 40.86

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by C1, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by LB, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
German Bank 1 2024-08-04 12,233 12,233 2023-08-06 2,687 2,687 2,021 2,021
Seal Island 1 2024-08-04 45,930 NA 2023-08-06 1,205 NA 929 NA
German Bank 2 NA NA NA 2023-08-20 4,930 4,406 3,282 2,887
German Bank 3 NA NA NA 2023-09-03 9,959 8,901 8,372 7,660
German Bank 4 NA NA NA 2023-09-13 16,266 13,203 15,011 12,498
Seal Island 2 NA NA NA 2023-08-20 1,918 NA 897 NA
Seal Island 3 NA NA NA 2023-09-03 2,063 NA 1,099 NA
Seal Island 4 NA NA NA 2023-09-13 5,636 NA 4,045 NA
German Bank 5 NA NA NA 2023-09-27 15,242 11,360 13,503 9,978
Seal Island 5 NA NA NA 2023-09-27 53,844 NA 42,269 NA
German Bank 6 NA NA NA 2023-10-11 23,614 20,057 26,563 23,390
Seal Island 6 NA NA NA 2023-10-11 15,261 NA 14,381 NA
German Bank 7 NA NA NA 2023-10-24 11,184 5,502 13,033 6,803
Seal Island 7 NA NA NA 2023-10-24 1,006 NA 1,087 NA
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 German Bank 83,882 66,116 81,785 65,237
2023 Seal Island 80,933 NA 64,707 NA
2024 German Bank 12,233 12,233 NA NA
2024 Seal Island 45,930 NA NA NA

Tagging, Plankton, and CTD Data

Summary map

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Janice II Lady Janice II
Set Number GB2024-01 GB2024-02
Ground GB GB
Date 04/08/2024 04/08/2024
Wind Direction (km/h) S S
Swell (m) 2 2
Air Temp (c) 20 20
Tow Details
Tow Start 19:12:00 19:27:00
Tow End 19:22:00 19:37:00
Start Lat 43.56933 43.56533
End Lat 43.56433 43.56000
Start Lon -66.35850 -66.35983
End Lon -66.36483 -66.36317
Avg Tow Depth (m) 3.191425 3.374661
Speed NA NA
Heading NA NA
Tide Direction against against
Other Data Collection
Flow Start 236916 263486
Flow End 263486 293230
No. Revolutions 26570 29744
Distance (m) 714.0156 799.3105
Volume 2243.080 2511.034
Secchi Disappear (m) 7 7
Secchi Reappear (m) 6 6

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is GB2024-01, which was against the tide and had an average depth of 3.1914252m. The second tow is GB2024-02, which was against the tide and had an average depth of 3.3746612m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 German Bank surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for German Bank.

Vessel Performance

Speed

Average vessel speed was 8.63. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.